Talk to the guy outside the Circle J near the gas station. He will give you the side quest and $1.14.
Inside the Circle J, you will see that slurpees cost $1.14 and you don't have enough to buy the condoms. Take a condom off the rack (they say 'Midas' on the front), take a cup, combine the condoms with the cup, and use the cup on the slurpee machine, go to the cash register and pay for it, then return to finish the side quest.